I've got a tamiya engine that I can get running but not for long. When the car starts it runs at its top for a few seconds, despite carb position, and then it cuts out. Anyone got any ideas why.
If you've tried setting your needles to their factory positions and that problem still persists, you might have a leak somewhere, either at the base of the carb, the head, or the backplate, most commonly.
There's a cool little test you can do that's similar to the way tire technicians check tires for pinhole leaks...pull the motor out, attach some fuel line to the carb. Get a cup of warm soapy water and a little paintbrush; cover the intake and exhaust ports with your fingers, seal 'em up real good. Then, while blowing air through the fuel line with your mouth, brush the soapy water around any parts where parts are joined, like the backplate, carb, head. Even do it around the HSN and the boot around the throttle and all that. If you see bubbles, you got a leak.
I had a Traxxas 2.5 I bought off eBay that ran like crap, if at all, and I was convinced it was a bad motor. Did that little soapy water bit, and it turned out the motor had an air leak right at the carb pin, you know, that bolt that you tighten down to hold the carb on. I put a little dab of gasket maker on the end of it, let it dry, and now that motors runs great, no problems.
Give that a shot, let me know how it works for ya. Any air leaks will basically render any tuning adjustments you make pointless.
